Ferromagnetism in dilute magnetic semiconductors and new materials for spintronics

Mn-doped polycrystals and single crystals of CdGeAs/sub 2/ have been synthesized by chemical technology and their semiconducting and magnetic properties were studied. Starting from around 3 mole% and above the Mn-ions begin to occupy the Ge/sup 4+/ sites, the complexes Mn/sup 2+/ +2p with weak bound holes p supply the hh in a valence band. This is confirmed by ESR, synchrotron measurements and X-ray analysis. Ferromagnetism was observed in samples at 3 and 6%Mn. In why-type samples, ferromagnetism is derived from the kinematic exchange between Mn/sup 2+/ + p complexes, while in (CdGe,Mn)As/sub 2/, ferromagnetism is governed by the kinematic exchange between Mn/sup 2+/ + 2p complexes mainly on the Ge-sites via empty states near the top of the valence band.